In a typical communications network, also referred to as e.g. a wireless communications network, a wireless communications system or a communications system, a device, communicates via a Radio Access Network (RAN) to one or more Core Networks (CNs).
The device may be a device by which a subscriber may access services offered by an operator's network and/or services outside operator's network to which the operators radio access network and core network provide access, e.g. access to the Internet. The device may be any device, mobile or stationary, enabled to communicate over a radio channel in the communications network, for instance but not limited to e.g. user equipment, mobile phone, smart phone, sensors, meters, vehicles, household appliances, medical appliances, media players, cameras, Machine to Machine (M2M) device or any type of consumer electronic, for instance but not limited to television, radio, lighting arrangements, tablet computer, laptop or Personal Computer (PC). The device may be portable, pocket storable, hand held, computer comprised, or vehicle mounted devices, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another device or a server.
Devices are enabled to communicate wirelessly in the communications network. The communication may be performed e.g. between two devices, between a devices and a regular telephone and/or between the devices and a server via the radio access network and possibly one or more core networks and possibly the Internet.
The radio access network covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g. a Radio Base Station (RBS), which in some radio access networks is also called evolved NodeB (eNB), NodeB, B node or base station. A cell is a geographical area where radio coverage is provided by the radio base station at a base station site. The base stations communicate with the devices within range of the base stations.
Charging is an important aspect in a communications network. The operators of the networks needs to manage the data traffic in the communications networks in order to make a fair revenue from the services it provides to its subscribers. The Policy and Charging Control (PCC) has been developed by the 3GPP in order to facilitate this. An important node in PCC is the Policy Control and Charging Rules Function (PCRF). The PCRF is a functional element that generates PCC rules, provides policy control and flow based charging control decisions. The PCRF interfaces with a Packet data network GateWay (PGW) and takes charging enforcement decisions on its behalf. The PCRF provides the PCC rules to a Policy and Charging Enforcement Function (PCEF). The PCEF is implemented in the PGW or a Serving GateWay (SGW) and is responsible for making sure that the PCC Rules are followed. It also provides usage measurement to support charging.
In order to support charging functionality and charging management in 3GPP network, the network performs online and/or offline charging using an Online Charging System (OCS) and an OFfline Charging System (OFCS). Offline charging is a charging mechanism where charging information does not affect, in real-time, the service rendered. Charging information for network resource usage is collected concurrently with that resource usage. Charging Data Record (CDR) files are generated by the network, which are then transferred to the network operator's billing domain for the purpose of subscriber billing. The OFCS receives events from a PCEF and generates CDRs for the billing system.
Online charging is a charging mechanism where charging information may affect, in real-time, the service rendered and therefore a direct interaction of the charging mechanism with bearer/session/service control etc is required. Charging information for network resource usage is collected concurrently with that resource usage in the same fashion as in offline charging. However, authorization for the network resource usage must be obtained by the network prior to the actual resource usage to occur. This authorization is granted by the OCS upon request from the network. When the network receives a network resource usage request, it collects the relevant charging information and generates a charging event towards the OCS in real-time. The OCS then returns an appropriate resource usage authorization. OCS provides credit management and grants credit to the PCEF based on time, traffic volume or chargeable events.
Offline and online charging may be performed simultaneously and/or independently for the same chargeable event. A chargeable event may be an activity that an operator wants to charge for. The activity may utilize communications network resources and/or related services for device to device communication, device to network communication, inter-network communication or mobility or similar.
A packet is an information unit comprising two types of information: control information and user data. The user data is also known as payload and is the part of the transmitted packet which is the purpose of the transmission, excluding the information sent together with it, i.e. the control information which is solely to facilitate delivery of the packet. A packet may be sent in DownLink (DL) or UpLink (UL). Downlink may be defined as transmission of signals from a Radio Access Network (RAN) access point or network to a device. Uplink may be defined as transmission of signals from a device to a RAN access point or network.
The General Packet Radio Service (GPRS) Tunnelling Protocol (GTP) is a group of IP-based communications protocols used to carry GPRS within e.g. Global System for Mobile communications (GSM), Universal Mobile Telecommunications System (UMTS) and Long Term Evolution (LTE) networks. GTP may be decomposed into separate protocols, GTP-Control plane (GTP-C), GTP User plane (GTP-U) and GTP′. GTP-C is used for control plane signaling between GPRS Support Nodes (GSN) in the core network. GTP-U is used for carrying user data within the core network and between the radio access network and the core network. GTP′ is a charging protocol. GTP may be used with User Datagram Protocol (UDP) or Transmission Control Protocol (TCP). There is a version 1 and a version 2 of GTP. The GTP-U, GTP-C and GTP′ have certain features in common. The structure of the GTP messages is the same with a GTP header following a UDP/TCP header. The GTP header has a plurality of fields, such as for example version field, Protocol Type (PT), Next Extension Header etc. At least some of these fields will be described in more detail later.
In a communications network, e.g. using 3GPP access, the radio access network is often the bottleneck for the throughput, i.e. payload packets may be dropped e.g. when there is congestion in the radio network, or when radio condition is poor. However such dropping is not feedback to the charging node and/or function, e.g. to the PGW/PCRF, which may represent a Policy and Charging Control (PCC) function. In other words, dropped packets are still charged. The PCC entities in a network cannot adjust the QoS policy to help to reduce such packets dropping, e.g. to improve QCI/ARP to let the device have a better position to compete with other devices about the available radio resources.
Packets may be dropped when one or more packets of data travelling across a network fail to reach their destination. In the downlink direction, some packets might be dropped by e.g. the eNB or SGW due to several reasons, for example, radio status, node congestion, transport status, etc. Especially in an Evolved Packet System (EPS) network, the downlink speed may reach up to 100M+ bps or more, so the downlink packets dropped by the eNB or the SGW have increased and may increase in the future. Even though the payload has not arrived at the device, it has been charged in a charging node such as e.g. the PGW, no matter online charging or offline charging.
FIG. 1 is a schematic block diagram illustrating points where packets may be dropped in a communications network 100. The communications network 100 in FIG. 1 comprises an E-UTRAN 101 communicating with a device 103 over a LTE-Uu interface. The E-UTRAN may be represented by for example an eNB. In the following, the terms E-UTRAN and eNB are used interchangeably with the reference number 101. E-UTRAN is an abbreviation for Evolved-Universal Terrestrial Radio Access Network. The E-UTRAN 101 is connected to a Mobility Management Entity (MME) 105 via a S1-MME interface. The MME 105 is connected to a Serving GPRS Support Node (SGSN) 108 via a S3 interface. The MME 105 is further connected to a Home Subscriber Server (HSS) 110 via an S6a interface and to a Serving GateWay (SGW) 113 via a S11 interface. The SGW 113 is connected to the E-UTRAN 101 via a S1-U interface. The SGW 113 is further connected to Universal Terrestrial Radio Access Network (UTRAN) 115 via a S12 interface and to a GSM EDGE Radio Access Network (GERAN) 118 via a S4 interface. EDGE is short for Enhanced Data rates for GSM Evolution. In addition, the SGW 113 is connected to a Packet data network GateWay (PGW) 120 via a S5 interface. The PGW 120 is connected to an OFfline Charging System (OFCS) 123 via a Gz interface and to a Policy and Charging Rules Function (PCRF) 125 via a Gx interface. The PGW 120 is connected via a SGi interface to an operator's IP services 128, e.g. such as IP Multimedia Subsystem (IMS), Packet Switch Streaming (PSS) or similar. The PCRF 125 is connected to the operators IP services 128 via an Rx interface.
As showed in FIG. 1, in the downlink direction (from the core network) to the device 103), the black circles indicate locations where payload packets may be dropped for some reasons, e.g. caused by radio situation, full buffer in the nodes, link congestion or similar. Even though the packets are dropped, the charging node and/or function, e.g. the PGW 120 comprising a PCEF, charges these dropped Packets by using a Charging Data Record (CDR), e.g. based on service type. CDR is a collection of information indicating a chargeable event for use in billing and accounting. Examples of a chargeable event may be time of call set-up, duration of the call, amount of data transferred, etc.
US 2012/0307730 discloses that a SGSN reports unsent octets of a Radio Network Controller (RNC) to a Gateway GPRS Support Node (GGSN) in connection with a message intended for other purposes. The SGSN creates information relating to unsuccessfully transmitted downlink data volume. The information is comprised in an information element which is pre-determined for unsuccessfully transmitted downlink data volume. The information element is referred to as “RNC Unsent Downlink Volume”. The information element is further comprised in one of a PDP context activation, PDP context modification and PDP context deactivation message. When the GGSN receives the RNC Unsent Downlink Volume from the SGSN, the GGSN generates CDR with a record of the volume of unsent downlink data. Thus, the possibility of overcharging for downlink data volume in the billing system may be prevented.
In an EPS network, as well as UMTS and GPRS network, a gateway is responsible for generating/sending CDR to OFCS for offline charging purpose.
In an existing method discarded packets are reported from the radio access network to the SGW/PGW. For example, 3GPP 32.298, version 11.4.0, section 5.1.2.2.53 describes the field “RNC Unsent Downlink Volume” for UMTS as follows: “This field contains the unsent downlink volume that the RNC has either discarded or forwarded to 2G-SGSN and already comprised in S-CDR. This field is present when RNC has provided unsent downlink volume count at RAB release and may be used by a downstream system to apply proper charging for this PDP context.” RAB is short for Radio Access Bearer. The “RNC unsent downlink volume” is only related to the RNC, which applies to UMTS. The eNB in EPS has the same function as the RNC in UMTS, however the 3GPP standard does not describe how to apply proper charging for the PDN connection/bearer context in EPS. Furthermore, it may be noted that the existing method only reports dropped information in relation to RAB release. It may also be noted that the existing method only supports PDP/bearer level.